People in all 50 U.S. states and more than 150 countries, from Germany to Australia, took to the streets to "to declare a climate emergency" the organizers said, and show politicians what action in line with climate science and justice means."

The strike was galvanized by a global youth movement, whose Friday school walkouts over the last year were themselves inspired by Thunberg's own three-week strike in August 2018 to demand climate action by the Swedish parliament.

People of all ages joined the global protest, though adults with their environmental organizations, climate negotiations and election campaigns took a little longer to gett on board. The Union of Concerned Scientists published an "Adult's Guide" to the climate strike to help parents of participants get up to speed.

But the kids are clearly leading on climate change and they're changing the way we talk about this global challenge, putting ethics at the center of the debate.

Climate change is an ethical problem

Economic assessments of climate change, such as cost-benefit analysis, have for years helped justify political procrastination. By discounting the importance of anticipated harms to people in the future, policymakers can argue that taking actions to address climate change today are too costly.

"When you think about the future today, you don't think beyond the year 2050," she said in a 2018 TED talk. "What we do or don't do right now will affect my entire life and the lives of my children and grandchildren."

Youth climate activists argue that "our house is on fire" and insist that world leaders act accordingly. They are attuned to the ecological consequences, intergenerational implications and international unfairness of climate change for all people living today.

Scholars in my field of environmental ethics have been writing about climate justice for decades. The arguments vary, but a key conclusion is that the burdens of responding to climate change should be divided equitably not borne primarily by the poor.

This notion of "common, but differentiated responsibilities" is a fundamental principle of equity outlined in the 1992 United Nations climate change treaty, which laid the groundwork for the many international climate negotiations that have occurred since.

Philosophers like Henry Shue have laid out the reasons that wealthy countries like the United States are morally bound not just to significantly cut their own carbon emissions but also help other countries adapt to a changing climate. That includes contributing financially to the development of climate-friendly energy sources that meet the pressing and near-term basic needs of developing countries.

Historically, wealthy countries have contributed the most and benefited the most from fossil fuel emissions. These same countries have the greatest financial, technological and institutional capacity to shift away from fossil fuels.

Meanwhile, poor countries are often most vulnerable to climate impacts like rising seas, more intense storms and eroding coastlines.

U.S. climate negotiators in particular have for decades pushed back against ethically grounded differentiated responsibilities and resisted top down mandatory emissions cuts, seeking a more politically palatable option: Voluntary emissions cuts determined by each country.

And some legal scholars say a climate policy based not on ethics but on self-interest might be more effective.

That includes inaction. The status quo a fossil fuel-dominated energy economy is making the rich richer and the poor poorer. Sticking with business as usual, the argument goes, places more importance on near-term benefits enjoyed by some than on the longer-term consequences many will suffer.

Polls show the youth are concerned and engaged. Youth activists are explicitly calling attention to the harm climate change is causing now and the harm it threatens for the future and demanding action. And they are working internationally, in a global movement of solidarity.

Scholarship on climate ethics is robust, but it has had limited effects on actual policy. Young people, on the other hand, are communicating the ethical issues clearly and loudly.

In doing so, they are demanding accountability from adults. They are asking us to consider what our resistance to change means for the world they will inherit.

So when my high school-aged daughter pulled a wrinkled climate strike flier out of her backpack recently, asking, "Can I skip school and go?"

I asked myself, "What am I saying if I say no?"

(The writer Marion Hourdequin is Professor of Philosophy, Colorado College).